Conditions for the existence of backward surface magnetostatic waves in a ferrite-insulator-metal structure

A theoretical analysis is made of the dispersion of surface magnetostatic waves (SMSWs) at different frequencies propagating in ferrite-insulator-metal (FIM) structures magnetized by a uniform magnetic field. It is established that depending on the ratio between the thicknesses of the ferrite and insulating layers in FIM structures, backward SMSWs exist in different frequency ranges and have different wave numbers and directions of propagation. The conditions for which backward SMSWs may be observed directly in FIM structures are determined. Pis’ma Zh. Tekh. Fiz. 24, 1–7 (July 12, 1998)     

Phase shift of surface magnetostatic waves propagating in nonuniformly magnetized ferrite films and ferrite-metal structures

It is shown that when surface magnetostatic waves propagate in a ferrite-metal structure magnetized by a linearly nonuniform field, the phase shift of these waves is many times greater than that accompanying propagation in a ferrite film and also in a ferrite-metal structure magnetized by a uniform field, and may reach extremely high values of tens of thousands of radians. This indicates that ferrite-metal structures magnetized by nonuniform fields are potentially useful for developing microwave shifters. Pis’ma Zh. Tekh. Fiz. 25, 79–84 (February 26, 1999)     

Solitons of a surface magnetostatic spin wave in a ferrite-insulator-metal structure

The nonlinear Schrodinger equation is analyzed in order to theoretically investigate nonlinear surface magnetostatic spin waves in a planar ferrite-insulator-metal structure. It is shown that for specific distances between the metal screen and the ferromagnetic film, pulses of surface magnetostatic spin waves may propagate as envelope solitons. Pis’ma Zh. Tekh. Fiz. 25, 48–54 (February 26, 1999)     

Wave propagation along domain walls in magnetic films

It is shown by theoretical analysis that domain walls can support two different types of waves denoted as "magnetostatic interface waves" and "wall displacement waves". The magnetostatic interface waves are similar in character to magnetostatic surface waves. The wall displacement waves are analogous to displacement waves on strings and to capillary waves on the surface of liquids, Dispersion relations are derived for both types of waves. The displacement waves are approximately dispersion free at high wavenumbers. At low wavenumbers their dispersion diagram reflects the incipient instability of the straight domain wall against sinusoidal displacement, which occurs as the field gradient is reduced.     

Trajectories of return surface magnetostatic waves in a ferrite-dielectric-metal structure magnetized by a nonuniform “ridge” field

Calculations are made of the trajectories of return surface magnetostatic waves (SMSWs) in a ferrite-dielectric-metal structure magnetized by a nonuniform “ridge” field. It is shown that there are four different types of trajectories. Conditions are determined for which the return SMSWs propagate in the direction opposite to the forward SMSWs and in the same direction as the forward SMSWs. Pis’ma Zh. Tekh. Fiz. 25, 61–66 (December 12, 1999)     

Mechanism of electric frequency tuning in composite resonators based on epitaxial ferrite films

A planar bilayer structure comprising an epitaxial film of yttrium iron garnet (YIG) ferrite film on a lead zirconate titanate (PZT) piezoelectric plate has been studied. It is shown both theoretically and experimentally that electric tuning of the resonant frequency is possible due to elastic-stress-induced variations of the field of uniaxial first-order anisotropy, while the field of uniaxial second-order anisotropy changes to a much lower degree. It is established that gluing of the ferrite and metal-coated piezoelectric layers rather insignificantly increases losses in the magnetostatic resonator.     

Characteristics of radiation generated during the conversion of backward bulk magnetostatic waves into electromagnetic waves

The directivity diagram of electromagnetic waves, generated during the propagation of backward bulk magnetostatic waves (BMSWs) in a ferrite plate tangentially magnetized by a decreasing field has been calculated using a model of the accelerated motion of magnetic charges. It is shown that the directivity diagram consists of two lobes, which are symmetric with respect to the ferrite plate surface and tilted back relative to the direction of backward BMSW propagation.     

Generation of electromagnetic waves by electrons rotating in a radial electrostatic field in free space

A theoretical analysis is made of mechanisms for the generation of electromagnetic waves by electrons rotating in a radial electrostatic field formed by a positively charged filament in free space. A dispersion equation is obtained to describe the interaction between the waves and nonrelativistic electrons. It is shown that electromagnetic fields can be generated by means of Čerenkov resonance. The frequencies and growth rates of the emitted waves are determined and their dependence on the parameters of the problem is investigated. Pis’ma Zh. Tekh. Fiz. 25, 1–4 (November 12, 1999)     

Nondispersive delay line on magnetostatic waves

A new approach to the design of a nondispersive delay line on magnetostatic waves is proposed, whereby the cascades operating on the surface waves and the backward volume waves have a common passband in the same magnetic system due to a difference in the crystallogrphic orientations of ferrite waveguides cut from a {100} yttrium iron garnet film. The possibility to obtain a pulse delay time of up to 113 ± 3 ns in a 300-MHz-wide frequency band is experimentally demonstrated. The central frequency of this band can be tuned within 4–6 GHz by changing the applied magnetic field.     

Characteristics of the excitation of ultrasonic waves by thin wafers of manganese zinc ferrite single crystals

It is suggested that thin wafers of a magnetostrictive material may be used as emitters of rf ultrasound. Single crystals of manganese zinc ferrite, which have high magnetostriction constants and low Foucault current losses, were used to investigate the orientational field dependences of the efficiency of excitation of acoustic waves having different polarizations. Some distinguishing features of the excitation of sound by single-crystal wafers compared with polycrystalline samples were observed, and the direction of propagation and polarization of the sound wave and its polarization relative to the crystallographic axes of manganese zinc ferrite with the highest conversion efficiency was identified. Pis’ma Zh. Tekh. Fiz. 24, 30–34 (March 26, 1998)     

Increasing thermal stability of devices employing backward volume magnetostatic waves in cubic ferrite films

A new method for the thermal stabilization of parameters of devices employing magnetostatic waves (MSWs) in ferrite films is proposed. The method is based on the dependence of the temperature coefficient of frequency on the magnetizing field orientation relative to the crystallographic axes of the film. Possibilities of the new method are demonstrated for the iron yttrium garnet films, the properties of which allow the thermal stability of frequency-selective MSW devices to be significantly improved.     

Magnetostatic surface waves on a moving domain boundary in a garnet ferrite crystal

The behavior of magnetostatic surface waves on a domain boundary uniformly propagating in a garnet ferrite crystal was theoretically studied. It was established that the boundary motion, while not affecting the magnetostatic surface wave structure, may significantly modify the wave spectrum.     

Magnetotemperature waves in electrically conducting media

A new type of temperature waves that appear in an electrically conducting medium placed in a magnetostatic field is discovered. The velocity of these magnetotemperature waves is determined by the coefficient of electrical conductivity λ of the conductor and greatly exceeds the velocity of temperature propagation by thermal conduction.     

Propagation characteristics of plane waves of defects in a viscoplastic medium

It is shown that dispersion is not observed in the propagation of a weakly damped wave, and dissipation is frequency-dependent. For strongly damped waves, dispersion and dissipation are observed. However, a wave in a viscoplastic medium decays over very short distances and the penetration depth of strongly damped waves of defects is bounded by the skinlayer thickness. Pis’ma Zh. Tekh. Fiz. 25, 91–94 (September 26, 1999)     

Dispersion characteristics of magnetostatic waves propagating at a ferrite/perovskite interface

The propagation of magnetostatic waves at the interface between an yttrium-iron-garnet (YIG) film and a layer of perovskite compound LaAlO₃, SrTiO₃, or YBa₂Cu₃O_7−x (YBCO) was experimentally studied. The microwave dispersion characteristics were measured at room temperature and at 77 K. An effective method for controlling the propagation speed and the phaseshift of magnetostatic waves in the YIG/YBCO structures is suggested. Specifically, the phaseshift at 3 GHz is changed by more than 1.5π by reducing the critical current density from 1 to 0.7× 10⁶ A/cm².     

Effect of ferrite magnonic crystal metallization on Bragg resonances of magnetostatic surface waves

It is experimentally established that metallization of the surface of a ferrite magnonic crystal destroys the Bragg resonances of magnetostatic surface waves by violating the conditions of phase synchronism of the incident wave and that reflected from the periodic surface structure.     

Interaction of relaxational waves with waves of a redistributing surfactant on a free surface of a liquid

Thermal capillary wave motion on a charged free surface of a liquid covered with a surfactant film gives rise to waves of redistributing charge (equalizing the electrical potential) and waves of the surfactant (equalizing the concentration of the surfactant). Numerical analysis of the dispersion equation shows that in some range of physical parameters the waves of charge interact with the waves of surfactant, forming two new branches of charge-concentration waves. Pis’ma Zh. Tekh. Fiz. 23, 25–31 (September 26, 1997)     

On the Nonuniqueness of Solutions to the Nonlinear Equations of Elasticity Theory

One-dimensional selfsimilar problems for waves in an elastic half-space generated by a sudden change of the boundary stress (the “piston” problem) and problems of disintegration of an arbitrary discontinuity are considered. For the case when small-amplitude waves are generated in a medium with small anisotropy a qualitative analysis shows that these problems have nonunique solutions when it is assumed that the solutions involve Riemann waves and evolutionary discontinuities. The above-mentioned problems are considered as limits of properly formulated problems for visco-elastic media when the viscosity tends to zero or (what is the same) that time tends to infinity. It is numerically found that all above-mentioned inviscid solutions can represent the asymptotics of visco-elastic solutions. The type of asymptotics depends on those details of the visco-elastic problem formulation which are absent when formulating inviscid selfsimilar problems. Similar considerations are made for elastic media with dispersion along with dissipation which are manifested in small-scale processes. In such media the number of available asymptotics (as t→∞) for the above-mentioned solutions depends on a relation between dispersion and dissipation and can be large. Thus, two possible causes for the nonuniqueness of solutions to the equations of elasticity theory are investigated.